Apparatus for preparing a coffee beverage

ABSTRACT

A coffee brewer contains a brewing unit in which coffee grounds having been poured in are compressed by a plunger driven by an actuator. Heated water flows through the compressed coffee grounds. A control device controls the actuator in accordance with signals of an angle of rotation sensor. The control device first moves the plunger against a stop in an ejection position to calibrate the sensor, then moves the plunger by a predetermined distance in a downwards direction into a pouring-in position. Afterwards the control device moves the plunger by a second distance into the brewing position, a length of the predetermined distance and the second distance corresponds to a number of pulses of the sensor which are stored in the memory. The control device subsequently moves the plunger by a third distance back into the ejection position in which the coffee grounds are removed from the plunger.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of patent application Ser. No.16/073,205, filed Jul. 26, 2018; which was a national stage application,under 35 U.S.C. § 371, of International application PCT/EP2017/000122,filed Feb. 1, 2017; the application also claims the priority, under 35U.S.C. § 119, of German patent application DE 10 2016 002 150, filedFeb. 25, 2016; the prior applications are herewith incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to an apparatus for preparing a coffee beverageand a method for preparing a coffee beverage using such an apparatus.

In the hot beverage machines currently in public use, by means of whichcoffee, espresso and other caffeinated hot drinks are provided inparticular, the use of brewing units is known that have a brewingchamber into which dried coffee powder is filled and in which adisplaceable plunger is arranged that compacts the powder after thechamber has been closed by means of a lid. Thereafter, hot water isapplied to the compressed powder to dissolve the flavors containedtherein and to then introduce the water as a hot drink into a cup via acorresponding dispensing unit.

In this connection, it is known from German patent DE 198 55 271 C1 tomove the plunger accommodated in the brewing chamber by means of aspindle drive comprising a simple electric motor that may be activatedby an electronic control device, the rotational angular position ofwhich is not detected during the movement of the plunger. In this case,the magnitude of the pressure exerted on the coffee powder by theplunger during the brewing process results purely accidentally from thefact that the electric motor is supplied with electric current by thecontrol device for a set period of time, in order to move it from thefilling position to the brewing position. The pressure exerted by theplunger on the coffee powder during the brewing process is subject tostrong fluctuations because the travel path and thus the end position ofthe plunger in this case is decided by the amount of coffee powder thathas been filled, the degree of grinding, and the frictional forces inthe gear via which the engine drives the plunger. However, as theapplicant has found, the pressure exerted by the plunger on the coffeepowder during the brewing process has a very great influence on theflavor quality of the coffee beverage, which is due, among other things,to increased exudation of bitter substances from the coffee powder dueto increased pressure; if the pressure generated by the plunger assumesa given ideal value, these bitter substances advantageously give greaterexpression to the flavor for a given type of coffee, manner of brewing,amount of coffee and degree of grinding. On the other hand, if thepressure exerted on the coffee powder by the plunger during the brewingprocess only slightly exceeds a certain threshold value that depends onthe aforementioned parameters, the bitter substances exude from thecoffee powder to a greater degree and detrimentally affect the qualityof the flavor in such a way that the drink is nearly undrinkable.

BRIEF SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide anapparatus and a method for preparing a coffee beverage by means of whichthe flavor quality of a coffee beverage, brewed in a brewing chamberusing a plunger acting on the coffee powder filled therein, may befurther improved.

This objective is achieved according to the invention as defined in theindependent claim(s). Other features which are considered ascharacteristic for the invention are set forth in the appended claims.

The invention will be described in the following with reference to thedrawings and in terms of a preferred embodiment.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 shows a schematic representation of the apparatus according tothe invention, wherein the plunger of the brewing unit has been moved tothe ejection position,

FIG. 2 shows the apparatus of FIG. 1 after the plunger has been moved tothe filling position,

FIG. 3 shows the apparatus of FIG. 1 after closing the lid,

FIG. 4 shows the apparatus of FIG. 1, wherein the plunger has been movedfrom the filling position to the brewing position while the coffeepowder has been compressed,

FIG. 5 shows the apparatus of FIG. 1 during the brewing process, and

FIG. 6 shows the apparatus of FIG. 1 after opening the lid and movingthe plunger to the ejection position.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1-6, the apparatus 1 for preparing a coffee beverageaccording to the invention comprises a brewing unit 2 having a brewingchamber 6 that may be closed by a lid 4, which, for example, may bemoved via an actuator (not shown) so as to open or close the brewingchamber 6 by means of the pins that are schematically indicated indashed lines and are laterally arranged on the lid and are guided in thecurved tracks.

In the brewing chamber 6, a plunger 14 may be moved up and down by meansof an electric actuator 10 via a gear mechanism 12 to compress coffeepowder 8 filled into the brewing chamber 6 before this powder ispercolated through by heated water introduced into the brewing chamber 6during the brewing process by means of an electric pump 16, and thewater then emerges as a coffee beverage from an outlet (not furthershown) of the brewing chamber 6. The movement of the plunger 14 iscontrolled by an electronic control device 18 which is connected to theactuator 10 in order to drive the plunger 14, and preferably alsocontrols the other components, such as the pump 16 for conveying theheated water to the brewing chamber 6, as well as the boiler (not shownin detail), or the grinder, etc.

The electronic control device 18 controls the electric actuator 10 forthis purpose based on the signals of a rotary encoder 20 associatedtherewith in such a way that the plunger 14 is moved from a fillingposition A (FIG. 3) for the coffee powder 8, while the coffee powder 8is being compressed, to a brewing position B (FIG. 5) and from there toan ejection position C (FIG. 7) for the coffee compact formed by thebrewing process in the brewing chamber 6. The apparatus according to theinvention is characterized in that the electronic control device 18first moves the plunger 14 for calibrating the rotary encoder 20 againsta stop 22 in the ejection position C (FIG. 1). From this ejectionposition C, the plunger 14 is subsequently moved by a predetermineddistance in the downward direction to the filling position A, the lengthof that distance corresponding to a first number of pulses of the rotaryencoder 20 stored in an electronic memory 24 of the electronic controldevice 18. After a predetermined filling time, in which the grinder (notshown in detail) is activated and the coffee powder is filled into theopen brewing chamber 6 from above, and after the lid 4 is closed, theelectronic control device 18 moves the plunger 14 by a second distancein the upward direction to the brewing position B, the length of thatdistance corresponding to the second number of pulses of the rotaryencoder 20 stored in the memory 24. After the electronic control device18 has received the corresponding second number of pulses from therotary encoder 20—in the present application the term “pulses” isintended to include any type of pulsed electronic signals, in particulardigital inputs and outputs—after a predetermined brewing time, thecontrol device 18 moves the plunger 14 from the brewing position B by apredetermined third distance back to the ejection position A, and inthis position, the compact is removed by an ejection mechanism (notshown in detail) from the plunger 14 after the lid 4 is opened.

The invention has the advantage that the calibration of the rotaryencoder 20 takes place with the lid open and with no pressure loadacting on the plunger 14. As a result, the errors in the calibrationprocess caused by frictional forces are kept as low as possible, whichin turn means that the positional error in the movement of the plunger14 to the brewing position B with the coffee powder 8 under compressionis also reduced, and the plunger may be moved to the brewing positionwith considerably higher accuracy. This increased accuracy in themovement of the plunger 14 to the brewing position while the coffeepowder is being compressed creates the possibility of reproduciblyadjusting, with an extremely high accuracy, the pressure that theplunger exerts on the coffee powder during the brewing process.

Due to the travel path of the plunger 14 when moving to the brewingposition B being derived solely from the pulses of the previouslycalibrated rotary encoder 20, the advantage results compared to a puretime-controlled positioning or a positioning via the received motorcurrent of the electric actuator 10, that the end position achieved forthe brewing process is almost independent of the frictional forces thatoccur.

Compared with a likewise conceivable measurement of the compressiveforce of the plunger on the coffee powder 8 by a pressure sensor, suchas a piezoelectric pressure sensor, the solution according to theinvention has the advantage that the determined compressive force thatin this case acts between the plunger and the drive element does notdepend on the temperature in the region of the sensor, but solely on thenumber of pulses generated by the rotary encoder 20 and supplied to thecontrol device 18. Because the number of pulses generated by the rotaryencoder is not affected by the temperature, which may vary considerablyin the brewing chamber 6 and also below the plunger 14 between thefilling of the brewing chamber and the brewing process, due to theintroduction of hot water, the pressure exerted on the coffee powder 8by the plunger 14 during the brewing process is subject to almost noinfluences from temperature.

In the preferred embodiment of the apparatus 1 according to theinvention, the electric actuator 10 is a direct current electric motorthat drives a spindle drive 12 b for a threaded spindle 12 c to whichthe plunger 14 is coupled, via a gearwheel 12 a fixed to the drive shaft10 a of the actuator. The rotary encoder 20 is a perforated disk orslotted disk rotatably coupled to the drive shaft 10 a of the electricmotor, which as shown in FIGS. 1 to 6 is preferably arranged on the endof the drive shaft 10 a opposite the gearwheel 12 a.

In the preferred embodiment of the invention, when moving the plungerfrom the initialization position shown in FIG. 1 or the ejectionposition A to the filling position shown in FIG. 2 via the maximumtravel path, the rotary encoder 20 may for example generate 680 pulses.Here, a 1 mm movement of the plunger 14, for example corresponds to 15pulses. It is understood that the number of pulses per millimeter oftravel path may be chosen differently by a corresponding reduction ofthe gear 12 or the spindle drive.

According to another idea underlying the invention, the apparatus 1 hasan input means 26 connected to the electronic control device 18, inparticular a first electrical switch, by the operation of which thenumber of pulses associated with the second distance may be increased ordecreased stepwise in the memory 24, in order to increase or decreasethe pressure that the plunger 14 applies to the coffee powder 8 in thebrewing position B.

The mode of operation of the apparatus 1 according to the invention willbe explained in greater detail below with reference to the method forpreparing a coffee beverage in which the above-described apparatus 1 isused.

In this case, the method according to the invention is characterized bythe following method steps:

-   -   a) inputting a desired type of coffee, coffee strength and a        flavor parameter associated with the type of coffee, and    -   b) increasing or decreasing value a stored in the memory 24 for        the second number of pulses generated by the rotary encoder 20        during the movement of the plunger 14 by the second distance        from the filling position A to the brewing position B based on        the input flavor parameter,    -   c) filling of an amount of coffee powder 8 associated with the        type and strength of coffee into the brewing chamber 6,    -   d) moving the lid 4 into the closed position,    -   e) moving the plunger 14 from the filling position A by the        second distance toward the ejection position C under compression        of the coffee powder, until the rotary encoder 14 generates the        second number of pulses that has been increased or decreased        based on the flavor parameter,    -   f) activating the pump 16 for a predetermined period of time to        introduce a predetermined amount of hot water into the brewing        chamber 6, and then deactivating the pump,    -   g) opening the lid 4 and moving the plunger 14 to the ejection        position A, and    -   h) removing the coffee compact from the plunger

In the method described above, it is particularly advantageous if afterthe deactivation of the pump 16, in order to squeeze the coffee compact,the plunger 14 is moved from the brewing position B to a squeezingposition D by a fourth distance toward the ejection position C until therotary encoder 14 has generated a number of pulses corresponding to thefourth distance, which is stored in the memory 24. By squeezing thecoffee powder 8 to which hot water was previously applied, the advantageresults that a dry coffee powder compact is formed that may be easilypushed down by the plunger 14 in the ejection position A by means of apusher or the like, which may also be attached to the lid 4, withoutleaving aqueous residues on the plunger that adversely affect the tasteof the coffee beverage in a subsequent brewing process.

Furthermore, it may be advantageous if in the method according to theinvention, after deactivation of the pump 16 and before opening the lid4, a valve arranged in the water supply line to the brewing chamber 6 isopened in order to draw off the brewing pressure generated in thebrewing chamber 6 during the brewing process from the brewing chamber 6before opening the lid 4.

According to another idea underlying the invention, the value stored inthe memory 24 for the second number of pulses is additionally increasedor decreased based on the coffee strength that was input and stored inthe memory 24, in such a way that when the amount of coffee powder 8filled into the brewing chamber 6 is increased, the second number ofpulses is reduced and the second distance is shortened accordingly. Thistakes into account the fact that there is no increase in the pressureexerted by the plunger 14 on the coffee powder 8 due to the increasedcoffee volume in the brewing position B, which would lead to leakage ofadditional bitter substances, but the position of the plunger 14 in thebrewing position is corrected accordingly, in order to obtain theoriginal preset pressure value, or the pressure value corrected via theinput means 26, despite the increased volume of coffee powder 8.

According to a further advantageous embodiment of the method accordingto the invention, the value stored in the memory 24 for the secondnumber of pulses is additionally increased or decreased based on a valuestored in the memory 24 for the type of coffee, in such a way that inthe case of a more heavily roasted coffee, the second number of pulsesis reduced and the second distance is shortened accordingly. Thisresults in the advantage that for different strengths of roasted typesof coffee, a corresponding correction of the pressure value may be madeby means of which the quality of the coffee beverage produced during thebrewing process may be adjusted individually to the preferences of therespective user.

In this context, it may furthermore be provided that the value stored inthe memory 24 for the second number of pulses may be stored togetherwith an individual user index as a fixed value in the memory 24 of theelectronic control device 18. In this case, it is of particularadvantage if additional input means 26 are furnished, via which thestored value may be retrieved by entering the individual user index fora next brewing process, in order to move the plunger 14 from the fillingposition A to the brewing position B by the second distance, until therotary encoder 20 has generated the second number of pulses retrievedfrom the memory 24.

Furthermore, it is advantageous for shortening the dispensing time ofthe coffee beverage, if the plunger 14 moves from the ejection positionC to the filling position A and/or from the filling position A to anintermediate position between the brewing position B and the fillingposition A at a speed higher than the speed at which the plunger 14 ismoved from the intermediate position to the brewing position.

Finally, according to another idea underlying the invention, it may beprovided that the change over time of the pulses generated by the rotaryencoder 20 during the movement of the plunger 14 from the fillingposition A to the brewing position B by the second distance is detectedby the electronic control device 18 and compared with a predeterminedthreshold value, in particular stored in memory 24, and in that theelectronic control device 18 generates a warning signal upon the valuefalling below the threshold value, which indicates to the operator thatthere is a lack of coffee in the coffee reservoir. By monitoring thechange over time of the pulses generated by the rotary encoder 20 duringthe movement of the plunger 14 over the second distance, which areproportional to the rotation rate of the drive motor, it is madepossible to detect the lack of coffee beans, or in simple apparatuseswithout grinders, the lack of coffee powder in the reservoir, in thesimplest way without an additional level sensor in the coffee reservoir.This is due to the fact that, if there is too little or no coffee powderthat has been filled into the brewing chamber in the filling position A,in the movement of the plunger 14 to the brewing position B nocompression-related resistance pressure is generated by the coffeepowder, which leads to a proper filling amount in that the rate ofrotation detected by the speed sensor 20 decreases and falls below thethreshold value. In other words, the absence of the decrease in the rateof rotation is determined by the electronic control device by comparingthe rate of rotation with a predetermined setpoint or threshold valueand in this case generating a warning signal that indicates to the userthat there is a lack of coffee beans or coffee powder in the reservoir.

The following is a summary list of reference numerals and thecorresponding structure used in the above description of the invention:

-   1 Apparatus-   2 Brewing unit-   4 Lid-   6 Brewing chamber-   8 Coffee powder-   10 Electric actuator-   10 a Drive shaft-   12 Mechanical gear-   12 a Gearwheel on drive shaft-   12 b Spindle drive-   12 c Threaded spindle-   14 Piston-   16 Pump-   18 Electronic control device-   20 Rotary encoder-   22 Stop-   24 Electronic memory-   26 Input means-   A Filling position of the plunger-   B Brewing position of the plunger-   C Ejection position of the plunger

1. An apparatus for preparing a coffee beverage, comprising: a lid; aplunger; an electric actuator; a gear mechanism; an electric pump; arotary encoder for outputting signals; a brewing unit having a brewingchamber that may be closed by said lid and receiving poured-in coffeegrounds, the coffee grounds being compressed by said plunger driven bysaid electric actuator via said gear mechanism, and compressed coffeegrounds being percolated through by heated water fed into said brewingchamber by said electric pump, said brewing chamber having an outletthrough which the heated water emerges; a stop; an ejector mechanism;and an electronic control device having a memory and controlling saidelectric actuator based on the signals of said rotary encoder such thatsaid plunger is moved from a filling position for the coffee grounds,while the coffee grounds are being compressed, to a brewing position andthen to an ejection position for a coffee compact formed in said brewingchamber by a brewing process, said electronic control device first movessaid plunger against said stop in the ejection position for calibratingsaid rotary encoder, then moves said plunger from the ejection positionby a predetermined distance in a downward direction to the fillingposition, a length of the predetermined distance corresponding to afirst number of pulses of said rotary encoder stored in said memory ofsaid electronic control device, and in that after a predeterminedfilling time said electronic control device moves said plunger in anupward direction by a second distance to the brewing position, a lengthof the second distance corresponding to a second number of pulses of therotary encoder stored in the memory, and in that after a predeterminedbrewing period said electronic control device moves said plunger a thirddistance back to the ejection position from the brewing position, and inthe ejection position, the coffee compact is removed by said plungerupon opening said lid, by means of said ejector mechanism.
 2. Theapparatus according to claim 1, further comprising a spindle drive;further comprising a threaded spindle; further comprising a gearwheel;wherein said electric actuator has a drive shaft; wherein said electricactuator is a direct current electric motor that drives said spindledrive for said threaded spindle to which said plunger is coupled, viasaid gearwheel fixed to said drive shaft of said electric actuator; andwherein said rotary encoder is a perforated disk or slotted diskrotatably coupled to said drive shaft of said electric actuator, whichis disposed on an end of said drive shaft opposite said gearwheel. 3.The apparatus according to claim 1, further comprising an input meansconnected to said electronic control device, by an operation of saidinput means a number of pulses associated with the second distance maybe increased or decreased stepwise in said memory, in order to increaseor decrease a pressure that said plunger applies to the coffee groundsin the brewing position.
 4. The apparatus according to claim 3, whereinsaid input means is an electrical switch.